1. Field of the Invention
The invention relates generally to interconnecting electronic devices and alternatively, to bonding conductors to opto-electronic devices.
2. Discussion of the Related Art
Opto-electronic devices are semiconductor devices that emit light, that detect incoming light, or that alter and re-emit light. Modern research and technology have made the use of opto-electronic devices commonplace in the lives of many individuals, although for many people such use is unknowing.
One major application of opto-electronic devices is in fiber optic communications. Over approximately the last two decades, fiber optic lines have taken over and transformed the long distance telephone industry. Optical fibers also play a dominant role in making the Internet available around the world. When optical fiber replaces copper wire for long distance calls and Internet traffic, costs are dramatically lowered and the rate at which information can be conveyed is increased.
Optical fibers convey voice, Internet traffic and other information digitally at speeds or data rates that currently range upward from one gigabit per second, and that are expected to reach hundreds of gigabits per second or more. In order to achieve these data rates, an opto-electronic device emits a beam of light that is turned on and off at the data rate that is at upward of one billion times each second. On the other end of the fiber optic cable, another opto-electronic device receives that beam of light and detects the pattern with which it is turned on and off.
Long distance fiber optical lines are commonplace. After a certain distance, light signals on optical fibers must be converted into electronic signals, electronically amplified and perhaps adjusted, and then re-emitted as light signals.
Opto-electronic emitters must receive from electronic devices the information they send optically, and opto-electronic detectors must send to electronic devices the information they receive optically. At least for the electronic devices that connect directly to the opto-electronic devices, this information must be sent at the same data rate as the information is carried on the optical fiber.
Unfortunately, at these data rates electronic interconnections can be problematic. The problems encountered include, among others, unintentional or parasitic effects. A wire that interconnects two electronic devices can create a small parasitic inductance and capacitance in the circuit, but at these data rates even small parasitic effects in circuits can have substantial effects on system performance. When such wires are placed close together, a parasitic coupling can be created between the signals on the two wires. Such parasitic effects distort the electronic signals on the wires, which can force the designers of opto-electronic systems to reduce the data rate at which the system operates, in order to reduce the effects of the distortions.
The electrical conductors used at these data rates should be as short as possible in order to minimize parasitic effects such as capacitance and inductance.
To increase bandwidth density, it is often preferable for the opto-electronic devices to be arranged in tightly spaced arrays. Bandwidth density measures the bandwidth of information that can be sent from, or received by, devices that fit within a unit of length along the side of a device, package or circuit board, or that fit within a unit of area of a device, package or circuit board. The former measure of bandwidth density can be expressed as gigabits per second per meter, and the latter measure as gigabits per second per square meter.
Preferably, the spacing used in such arrays is determined by the optics part of the system, not the electronic devices that drive the opto-electronic devices. Arrays of opto-electronic devices may be used to transmit light signals that are conveyed by a ribbon-like bundle of optical fibers. Or, a single optical fiber that carries different signals at different wavelengths may be used with such an array, where each opto-electronic device in the array operates at a different wavelength.
The electrical conductors used at these data rates should be as uniformly spaced as possible. This both prevents accidental connections between the conductors and minimizes parasitic coupling between the conductors.
Other problems arise from the requirement that such opto-electronic devices be produced in volume. Millions of opto-electronic devices are in use today. Production rates in excess of one million units per month are occurring, or are projected for the immediate future. In order to meet these demands for volume production, the process of interconnecting opto-electronic devices with electronic devices must be inexpensive and reliable. This suggests that the interconnection process be highly automated.